Liquid-crystalline medium and liquid-crystal display comprising the same

ABSTRACT

The invention relates to a liquid-crystalline medium, having particular dielectric properties, in that it has:
         either a dielectric constant perpendicular to the director (∈ ⊥ ) in the range of 2 or more to less 8 or less and at the same time a ratio of the dielectric constant perpendicular to the director (∈ ⊥ ) to the dielectric anisotropy (Δ∈), i.e. (∈ ⊥ /Δ∈) of 1.0 or more or   or a dielectric constant perpendicular to the director (∈ ⊥ ) of 8 or more and a dielectric anisotropy (Δ∈) of 26 or less and
 
preferably comprises one or more compounds having a high dielectric constant perpendicular to the director (∈ ⊥ ) and a high average dielectric constant (∈ av. ). These compounds are suitable for use in an electro-optical display, particularly in an active-matrix display based on the IPS or FFS effect.

The present invention relates to novel liquid crystalline media, in particular for use in liquid-crystal displays, and to these liquid-crystal displays, particularly to liquid-crystal displays which use the IPS (in-plane switching) or, preferably, the FFS (fringe field switching) effect using dielectrically positive liquid crystals. The last one is also called SG-FFS (super grip FFS) effect occasionally. For this effect dielectrically positive liquid crystals are used, which comprise one or more compounds having at the same time a high dielectric constant parallel to the molecular director and perpendicular to the molecular director, leading to a large average dielectric constant and a high dielectric ratio and, preferably, to a relatively small dielectric anisotropy at the same time. The liquid crystalline media optionally additionally comprise dielectrically negative, dielectrically neutral compounds or both. The liquid crystalline media are used in a homogeneous (i.e. planar) initial alignment. The liquid-crystal media according to the invention have a positive dielectric anisotropy and comprise compounds having at the same time large dielectric constants parallel and perpendicular to the molecular director.

The media are distinguished by a particularly high transmission and reduced response time in respective displays, which is brought about by their unique combination of physical properties, especially by their dielectric properties and in particular by their high ratio of (∈_(⊥)/∈_(av.)) respectively of the high values of their dielectric ratio (∈_(⊥)/Δ∈). This also leads to their excellent performance in the displays according to the invention.

IPS and FFS displays using dielectrically positive liquid crystals are well known in the field and have been widely adopted for various types of displays like e.g. desk top monitors and TV sets, but also for mobile applications.

However, recently, IPS and in particular FFS displays using dielectrically negative liquid crystals are widely adopted. The latter ones are sometimes also called or UB-FFS (ultra bright FFS). Liquid crystalline media used for UB-FFS have a dielectric anisotropy of −0.5 or less, preferably −1.5 or less. Such displays are disclosed e.g. in US 2013/0207038 A1. These displays are characterized by a markedly increased transmission compared to the previously used IPS- and FFS displays, which contain dielectrically positive liquid crystals. Displays using dielectrically negative liquid crystals, however, have the severe disadvantage of requiring a higher operation voltage than the respective displays using dielectrically positive liquid crystals.

Liquid crystalline media used for HB-FFS (high brightness FFS) comprising both dielectrically negative and dielectrically positive liquid crystalline compounds, respectively mesogenic compounds are disclosed e.g. in US 2013/0207038 A1. These media feature rather large values of ∈_(⊥) and of ∈_(av.) already, however, their ratio of (∈_(⊥)/Δ∈) is relatively small. Liquid crystalline media used for HB-FFS have a dielectric anisotropy of 0.5 or more, preferably −1.5 or more.

According to the present application, however, the IPS or the FFS effects with dielectrically positive liquid crystalline media in a homogeneous alignment are preferred.

Industrial application of this effect in electro-optical display elements requires LC phases which have to meet a multiplicity of requirements. Particularly important here are chemical resistance to moisture, air and physical influences, such as heat, radiation in the infrared, visible and ultraviolet regions, and direct (DC) and alternating (AC) electric fields.

Furthermore, LC phases which can be used industrially are required to have a liquid-crystalline mesophase in a suitable temperature range and low viscosity.

None of the series of compounds having a liquid-crystalline mesophase that have been disclosed hitherto includes a single compound which meets all these requirements. Mixtures of two to 25, preferably three to 18, compounds are therefore generally prepared in order to obtain substances which can be used as LC phases.

Matrix liquid-crystal displays (MLC displays) are known. Non-linear elements which can be used for individual switching of the individual pixels are, for example, active elements (i.e. transistors). The term “active matrix” is then used, where in general use is made of thin-film transistors (TFTs), which are generally arranged on a glass plate as substrate.

A distinction is made between two technologies: TFTs comprising compound semiconductors, such as, for example, CdSe, or metal oxides like ZnO or TFTs based on polycrystalline and, inter alia, amorphous silicon.

The latter technology currently has the greatest commercial importance worldwide.

The TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counter electrode on its inside. Compared with the size of the pixel electrode, the TFT is very small and has virtually no adverse effect on the image. This technology can also be extended to fully color-capable displays, in which a mosaic of red, green and blue filters is arranged in such a way that a filter element is located opposite each switchable pixel.

The TFT displays most used hitherto usually operate with crossed polarizers in transmission and are backlit. For TV applications, ECB (or VAN) cells or FFS cells are used, whereas monitors usually use IPS cells or TN (twisted nematic) cells, and notebooks, laptops and mobile applications usually use TN, VA or FFS cells.

The term MLC displays here encompasses any matrix display having integrated non-linear elements, i.e., besides the active matrix, also displays with passive elements, such as varistors or diodes (MIM=metal-insulator-metal).

MLC displays of this type are particularly suitable for TV applications, monitors and notebooks or for displays with a high information density, for example in automobile manufacture or aircraft construction. Besides problems regarding the angle dependence of the contrast and the response times, difficulties also arise in MLC displays due to insufficiently high specific resistance of the liquid-crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp. 141 ff., Paris; STROMER, M., Proc. Eurodisplay 84, September 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, pp. 145 ff., Paris]. With decreasing resistance, the contrast of an MLC display deteriorates. Since the specific resistance of the liquid-crystal mixture generally drops over the life of an MLC display owing to interaction with the inside surfaces of the display, a high (initial) resistance is very important for displays that have to have acceptable resistance values over a long operating period.

Displays which use the ECB effect have become established as so-called VAN (vertically aligned nematic) displays, besides IPS displays (for example: Yeo, S. D., Paper 15.3: “An LC Display for the TV Application”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 758 and 759) and the long-known TN displays, as one of the three more recent types of liquid-crystal display that are currently the most important, in particular for television applications.

The most important designs may be mentioned here: MVA (multi-domain vertical alignment, for example: Yoshide, H. et al., Paper 3.1: “MVA LCD for Notebook or Mobile PCs . . . ”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 6 to 9, and Liu, C. T. et al., Paper 15.1: “A 46-inch TFT-LCD HDTV Technology . . . ”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 750 to 753), PVA (patterned vertical alignment, for example: Kim, Sang Soo, Paper 15.4: “Super PVA Sets New State-of-the-Art for LCD-TV”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 760 to 763) and ASV (advanced super view, for example: Shigeta, Mitzuhiro and Fukuoka, Hirofumi, Paper 15.2: “Development of High Quality LCDTV”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pp. 754 to 757). More modern versions of the VA effect, are the so called PAVA (photo-alignment VA) and PSVA (polymerstabilized VA).

In general form, the technologies are compared, for example, in Souk, Jun, SID Seminar 2004, Seminar M-6: “Recent Advances in LCD Technology”, Seminar Lecture Notes, M-6/1 to M-6/26, and Miller, Ian, SID Seminar 2004, Seminar M-7: “LCD-Television”, Seminar Lecture Notes, M-7/1 to M-7/32. Although the response times of modern ECB displays have already been significantly improved by addressing methods with overdrive, for example: Kim, Hyeon Kyeong et al., Paper 9.1: “A 57-in. Wide UXGA TFT-LCD for HDTV Application”, SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pp. 106 to 109, the achievement of video-compatible response times, in particular in the switching of grey shades, is still a problem which has not yet been solved to a satisfactory extent.

ECB displays, like ASV displays, use liquid-crystalline media having negative dielectric anisotropy (Δ∈), whereas TN and to date all conventional IPS displays use liquid-crystalline media having positive dielectric anisotropy. However, presently there is an increasing demand for IPS and FFS displays utilizing dielectrically negative liquid crystalline media.

In liquid-crystal displays of this type, the liquid crystals are used as dielectrics, whose optical properties change reversibly on application of an electrical voltage.

Since in displays in general, i.e. also in displays in accordance with these mentioned effects, the operating voltage should be as low as possible, use is made of liquid-crystal media which are generally predominantly composed of liquid-crystal compounds, all of which have the same sign of the dielectric anisotropy and have the highest possible value of the dielectric anisotropy. In general, at most relatively small proportions of neutral compounds and if possible no compounds having a sign of the dielectric anisotropy which is opposite to that of the medium are employed. In the case of liquid-crystal media having negative dielectric anisotropy e.g. for ECB or UB-FFS displays, predominantly compounds having negative dielectric anisotropy are thus employed. The respective liquid-crystalline media employed generally consist predominantly and usually even essentially of liquid-crystal compounds having negative dielectric anisotropy.

In the media used in accordance with the present application, significant amounts of dielectrically positive liquid-crystal compounds and generally only very small amounts of dielectrically compounds or even none at all are typically employed, since in general the liquid-crystal displays are intended to have the lowest possible addressing voltages. At the same time small amounts of dielectrically neutral compounds may be beneficially used in some cases.

US 2013/0207038 A1 discloses liquid crystalline media for HB-FFS displays proposing to improve the performance of the FFS displays using liquid crystals having a positive dielectric anisotropy by the additional incorporation of dielectrically negative liquid crystals. This, however, leads to the necessity of a compensation of the negative contribution of these compounds to the overall dielectric anisotropy of the resultant media. To this end, either the concentration of the dielectrically positive materials has to be increased, which, in turn, leaves less room for the use of dielectrically neutral compounds as diluters in the mixtures, or, alternatively, compounds with a stronger positive dielectric anisotropy have to be used. Both of these alternatives have the strong drawback of increasing the response time of the liquid crystals in the displays.

Liquid crystalline media having a positive dielectric anisotropy for IPS and FFS displays have already been disclosed. In the following some examples will be given.

CN 104232105 A discloses liquid crystalline media with a positive dielectric anisotropy having dielectric ratios (∈_(⊥)/Δ∈) of up to 0.7.

WO 2014/192390 also discloses liquid crystalline media with a positive dielectric anisotropy having rather high values of ∈_(∥), but having dielectric ratios (∈_(⊥)/Δ∈) of only about 0.5.

WO 2015/007131 discloses liquid crystalline media with a positive dielectric anisotropy, some of which have a dielectric ratio (∈_(⊥)/Δ∈) of about 0.7 and slightly above, up to 0.88.

Obviously, the range of the nematic phase of the liquid-crystal mixture must be sufficiently broad for the intended application of the display.

The response times of the liquid-crystal media in the displays also have to be improved, i.e. reduced. This is particularly important for displays for television or multimedia applications. In order to improve the response times, it has repeatedly been proposed in the past to optimize the rotational viscosity of the liquid-crystal media (γ₁), i.e. to achieve media having the lowest possible rotational viscosity. However, the results achieved here are inadequate for many applications and therefore make it appear desirable to find further optimization approaches.

Adequate stability of the media to extreme loads, in particular to UV exposure and heating, is very particularly important. In particular in the case of applications in displays in mobile equipment, such as, for example, mobile telephones, this may be crucial.

Besides their relatively poor transmission and their relatively long response times, the MLC displays disclosed hitherto, they have further disadvantages. These are e.g. their comparatively low contrast, their relatively high viewing-angle dependence and the difficulty in the reproduction of grey scales in these displays, especially when observed from an oblique viewing angle, as well as their inadequate VHR and their inadequate lifetime. The desired improvements of the transmission of the displays and of their response times are required in order to improve their energy efficiency, respectively their capacity to render rapidly moving pictures.

There thus continues to be a great demand for MLC displays having very high specific resistance at the same time as a large working-temperature range, short response times and a low threshold voltage, with the aid of which various grey shades can be produced and which have, in particular, a good and stable VHR.

Thus, an object of the invention is to provide MLC displays, not only for monitor and TV applications, but also for mobile applications such as e.g. telephones and navigation systems, which are based on the ECB, IPS or FFS effect, that do not have the disadvantages indicated above, or only do so to a lesser extent, and at the same time have very high specific resistance values. In particular, it must be ensured for mobile telephones and navigation systems that they also work at extremely high and extremely low temperatures.

Upon further study of the specification and appended claims, other objects, aspects and advantages of the invention will become apparent.

Surprisingly, it has been found that it is possible to achieve liquid-crystal displays which have, in particular in IPS and FFS displays, a low threshold voltage with short response times, a sufficiently broad nematic phase, favorable, relatively low birefringence (An) and, at the same time, a high transmission, good stability to decomposition by heating and by UV exposure, and a stable, high VHR (voltage holding ratio) if use is made in these display elements of nematic liquid-crystal mixtures which comprise at least one compound, preferably two or more compounds of formula I, preferably selected from the group of the compounds of the sub-formulae I-1, I-2, I-3 and I-4, particularly preferably the sub-formulate I-2 and/or I-3 and/or I-4, more preferably I-2 and/or I-4, and preferably additionally at least one compound, preferably two or more compounds, selected from the group of the compounds of the formulae Hand III, the former preferably of formula II-1 and/or II-2, and/or at least one compound, preferably two or more compounds selected from the group of formulae IV and/or V and, preferably, one or more compounds selected from the group of formulae VII to IX (all formulae as defined herein below).

Media of this type can be used, in particular, for electro-optical displays having active-matrix addressing for IPS—or FFS displays.

The invention thus relates to a liquid-crystalline medium on a mixture of polar compounds comprising one or more compounds having either

-   -   a dielectric constant perpendicular to the director (∈_(⊥)) in         the range of 2 or more, to 8 or less, and a dielectric ratio of         the dielectric constant perpendicular to the director to the         dielectric anisotropy (∈_(⊥)/Δ∈) of 1.0 or more or     -   a dielectric constant perpendicular to the director (∈_(⊥)) of         8.0 or more, preferably of 26 or less and, preferably,         additionally also a dielectric ratio of the dielectric constant         perpendicular to the director to the dielectric anisotropy         (∈_(⊥)/Δ∈) of 1.0 or more.

The ratio of the dielectric constant perpendicular to the director to the dielectric anisotropy (∈_(⊥)/Δ∈) of 1.0 or more corresponds to the ratio of the dielectric constant parallel (∈_(∥)) to the director to dielectric constant perpendicular (∈_(⊥)) to the director, i.e. to the ratio of (∈_(∥)/∈_(⊥)) of 2.0 or less.

The media according to the present invention preferably additionally comprise one or more compounds selected from the group of compounds of formulae II and III, preferably one or more compounds of formula II, more preferably in addition one or more compounds of formula III and, most preferably, additionally one or more compounds selected from the group of the compounds of formulae IV and V and, again preferably, one or more compounds selected from the group of compounds of formulae VI to IX (all formulae as defined below).

The mixtures according to the invention exhibit very broad nematic phase ranges with clearing points ≧70° C., very favorable values for the capacitive threshold, relatively high values for the holding ratio and at the same time good low-temperature stabilities at −20° C. and −30° C., as well as very low rotational viscosities. The mixtures according to the invention are furthermore distinguished by a good ratio of clearing point and rotational viscosity and by a relatively high positive dielectric anisotropy.

Now, it has been found surprisingly that LCs of the FFS type using liquid crystals with positive dielectric anisotropy may be realized using specially selected liquid crystalline media. These media are characterized by a particular combination of physical properties. Most decisive amongst these are their dielectric properties and here a high average dielectric constant (∈_(av.)), a high dielectric constant perpendicular to the director of the liquid crystal molecules (∈_(⊥)), a high value of the dielectric anisotropy (Δ∈), and, in particular, a relatively high ratio of these latter two values: (∈_(⊥)/Δ∈).

Preferably, the liquid-crystalline media according to the present invention, on the one hand, have a value of the dielectric anisotropy of 0.5 or more, preferably of 1.0 or more preferably of 1.5 or more. At the other hand, they preferably have a dielectric anisotropy of 26 or less.

Preferably, the liquid-crystalline media according to the present invention, on the one hand, have a value of the dielectric constant perpendicular to the director of 2 or more, more preferably of 8 or more and, on the other hand preferably of 20 or less.

The liquid crystalline media according to the present invention preferably have a positive dielectric anisotropy, preferably in the range from 1.5 or more to 20.0 or less, more preferably in the range from 3.0 or more to 8.0 or less and, most preferably in the range from 4.0 or more to 7.0 or less.

The liquid crystalline media according to the present invention preferably have a dielectric constant perpendicular to the director of the liquid crystal molecules (∈_(⊥)) of 5.0 or more, more preferably of 6.0 or more, more preferably of 7.0 or more, more preferably of 8.0 or more, more preferably of 9 or more and, most preferably, of 10.0 or more.

The liquid crystalline media according to the present invention preferably have a dielectric ratio (∈_(⊥)/Δ∈) of 1.0 or more, more preferably of 1.5 or more and, most preferably, of 2.0 or more.

In a preferred embodiment of the present invention the liquid crystalline medium preferably comprises

-   a) one or more compounds having both a high dielectric constant     perpendicular to the director and parallel to the director,     preferably selected from the group of compounds of formula I,     preferably in a concentration in the range from 1% to 60%, more     preferably in the range from 5% to 40%, particularly preferably in     the range from 8% to 35%, based on the total weight of the liquid     crystalline medium,

in which

denotes

denotes

-   n denotes 0 or 1, -   R¹¹ and R¹² independently of each other denote alkyl, alkoxy,     fluorinated alkyl or fluorinated alkoxy, preferably having 1 to 7 C     atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl     having 2 to 7 C atoms and preferably alkyl, alkoxy, alkenyl or     alkenyloxy, most preferably alkyl, alkoxy or alkenyloxy, and R¹¹     alternatively denotes R¹ and R¹² alternatively denotes X¹, -   R¹ denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy     preferably having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl     or fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or     alkenyl, and -   X¹ denotes F, Cl, fluorinated alkyl, fluorinated alkenyl,     fluorinated alkoxy or fluorinated alkenyloxy, the latter four groups     preferably having 1 to 4 C atoms, preferably F, Cl, CF₃ or OCF₃, in     particular for formulae I-1 and I-2 preferably F and for formula I-4     preferably OCF₃, and -   b) one or more dielectrically positive compounds selected from the     group of compounds of formulae II and III, preferably of compounds     having a dielectric anisotropy of greater than 3 each:

in which

-   R² denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy     having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or     fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or     alkenyl,

-   -   on each appearance, independently of one another, denote

preferably

-   L²¹ and L²² denote H or F, preferably L²¹ denotes F, -   X² denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C     atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms,     preferably F, Cl, —OCF₃, —O—CH₂CF₃, —O—CH═CH₂, —O—CH═CF₂ or —CF₃,     very preferably F, Cl, —O—CH═CF₂ or —OCF₃, -   m denotes 0, 1, 2 or 3, preferably 1 or 2 and particularly     preferably 1, -   R³ denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy     having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or     fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or     alkenyl,

-   -   on each appearance, independently of one another, are

preferably

-   L³¹ and L³², independently of one another, denote H or F, preferably     L³¹ denotes F, -   X³ denotes halogen, halogenated alkyl or alkoxy having 1 to 3 C     atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms,     preferably F, Cl, —OCF₃, —OCHF₂, —O—CH₂CF₃, —O—CH═CF₂, —O—CH═CH₂ or     —CF₃, very preferably F, Cl, —O—CH═CF₂, —OCHF₂ or —OCF₃, -   Z³ denotes —CH₂CH₂—, —CF₂CF₂—, —COO—, trans-CH═CH—, trans-CF═CF—,     —CH₂O— or a single bond,     -   preferably —CH₂CH₂—, —COO—, trans-CH═CH— or a single bond, and         very preferably —COO—, trans-CH═CH— or a single bond, and -   n denotes 0, 1, 2 or 3, preferably 1, 2 or 3 and particularly     preferably 1, and -   c) optionally one or more dielectrically neutral compounds selected     from the group of formulae IV and V:

-   in which -   R⁴¹ and R⁴², independently of one another, have the meaning     indicated above for R² under formula II, preferably R⁴¹ denotes     alkyl and R⁴² denotes alkyl or alkoxy or R⁴¹ denotes alkenyl and R⁴²     denotes alkyl,

-   -   independently of one another and, if

occurs twice,

-   -   also these independently of one another, denote

-   -   preferably one or more of

-   -   denotes or denote,

-   Z⁴¹ and Z⁴², independently of one another and, if Z⁴¹ occurs twice,     also these independently of one another,     -   denote —CH₂CH₂—, —COO—, trans-CH═CH—, trans-CF═CF—, —CH₂O—,         —CF₂O—, —C≡C— or a single bond, preferably one or more thereof         denotes/denote a single bond, and -   p denotes 0, 1 or 2, preferably 0 or 1, and -   R⁵¹ and R⁵², independently of one another, have one of the meanings     given for R²¹ and R²² and preferably denote alkyl having 1 to 7 C     atoms, preferably n-alkyl, particularly preferably n-alkyl having 1     to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy,     particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl,     alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to     4 C atoms, preferably alkenyloxy,

-   -   if present, each, independently of one another, denote

preferably

preferably

denotes

and, if present,

preferably denotes

-   Z⁵¹ to Z⁵³ each, independently of one another, denote —CH₂—CH₂—,     —CH₂—O—, —CH═CH—, —C≡C—, —COO— or a single bond, preferably     —CH₂—CH₂—, —CH₂—O— or a single bond and particularly preferably a     single bond, -   i and j each, independently of one another, denote 0 or 1, -   (i+j) preferably denotes 0, 1 or 2, more preferably 0 or 1 and, most     preferably, 1. -   d) again optionally, either alternatively or additionally, one or     more dielectrically negative compounds selected from the group of     formulae VI to IX:

-   wherein -   R⁶¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably a straight-chain alkyl radical, more preferably an     n-alkyl radical, most preferably propyl or pentyl, an unsubstituted     alkenyl radical having 2 to 7 C atoms, preferably a straight-chain     alkenyl radical, particularly preferably having 2 to 5 C atoms, an     unsubstituted alkoxy radical having 1 to 6 C atoms, or an     unsubstituted alkenyloxy radical having 2 to 6 C atoms, -   R⁶² denotes an unsubstituted alkyl radical having 1 to 7 C atoms, an     unsubstituted alkoxy radical having 1 to 6 C atoms, or an     unsubstituted alkenyloxy radical having 2 to 6 C atoms, and -   I denotes 0 or 1, -   R⁷¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably a straight-chain alkyl radical, more preferably an     n-alkyl radical, most preferably propyl or pentyl, or an     unsubstituted alkenyl radical having 2 to 7 C atoms, preferably a     straight-chain alkenyl radical, particularly preferably having 2 to     5 C atoms, -   R⁷² denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably having 2 to 5 C atoms, an unsubstituted alkoxy radical     having 1 to 6 C atoms, preferably having 1, 2, 3 or 4 C atoms, or an     unsubstituted alkenyloxy radical having 2 to 6 C atoms, preferably     having 2, 3 or 4 C atoms, and

denotes

-   R⁸¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably a straight-chain alkyl radical, more preferably an     n-alkyl radical, most preferably propyl or pentyl, or an     unsubstituted alkenyl radical having 2 to 7 C atoms, preferably a     straight-chain alkenyl radical, particularly preferably having 2 to     5 C atoms, -   R⁸² denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably having 2 to 5 C atoms, an unsubstituted alkoxy radical     having 1 to 6 C atoms, preferably having 1, 2, 3 or 4 C atoms, or an     unsubstituted alkenyloxy radical having 2 to 6 C atoms, preferably     having 2, 3 or 4 C atoms,

denotes

-   -   preferably

-   -   more preferably

-   Z⁸ denotes —(C═O)—O—, —CH₂—O—, —CF₂—O— or —CH₂—CH₂—, preferably     —(C═O)—O— or —CH₂—O—, and -   o denotes 0 or 1, -   R⁹¹ and R⁹² independently of one another have the meaning given for     R⁷² above, -   R⁹¹ preferably denotes an alkyl radical having 2 to 5 C atoms,     preferably having 3 to 5 C atoms, -   R⁹² preferably denotes an alkyl or alkoxy radical having 2 to 5 C     atoms, more preferably an alkoxy radical having 2 to 4 C atoms, or     an alkenyloxy radical having 2 to 4 C atoms.

denotes

-   p and q independently of each other denote 0 or 1, and -   (p+q) preferably denotes 0 or 1, and in the case where

denotes

-   -   alternatively, preferably p=q=1.

The liquid-crystalline media in accordance with the present application preferably have a nematic phase.

Preferably the compounds of formula I are selected from the group of compounds of formulae I-1 to I-4:

in which

-   R¹¹ and R¹² independently of each other denote alkyl, alkoxy,     fluorinated alkyl or fluorinated alkoxy, preferably having 1 to 7 C     atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl     having 2 to 7 C atoms, and preferably alkyl, alkoxy, alkenyl or     alkenyloxy, most preferably alkoxy or alkenyloxy, -   R¹ denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy     preferably having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl     or fluorinated alkenyl having 2 to 7 C atoms and preferably alkyl or     alkenyl, and -   X¹ denotes F, Cl, CN, NCS, fluorinated alkyl, fluorinated alkenyl,     fluorinated alkoxy or fluorinated alkenyloxy, the latter four groups     preferably having 1 to 4 C atoms, preferably F, Cl, CF₃ or OCF₃, in     particular for formulae I-1 and I-2 preferably F and for formula I-4     preferably OCF₃.

The compounds of formula I-3 are prepared according to WO 02/055463 and compounds of the formula I-3 containing two alkoxy groups (R¹¹=>R¹—O; R¹²=>R²—O) are preferably prepared starting from the basic compound dibenzofuran according to the following scheme: (Scheme 1).

The compounds of formula I-3 containing one alkoxy group (R¹—O) and one alkyl group (R²), (R¹¹=>R¹—O; R¹²=>R²) are preferably prepared starting) from the basic compound dibenzofuran according to the following scheme: (Scheme 2).

The compounds of formula I-3 containing two alkyl groups (R¹¹=>R¹; R¹²=>R²) are preferably prepared starting from the basic compound dibenzofuran according to the following scheme: (Scheme 3).

The compounds of formula I-4 are preferably prepared e.g. according to the following scheme.

The invention furthermore relates to the use of liquid-crystal mixtures and liquid-crystalline media according to the invention in IPS and FFS displays, in particular the use in SG-FFS displays containing a liquid-crystalline medium, for improving the response times and/or the transmission.

The invention furthermore relates to a liquid-crystal display containing a liquid-crystalline medium according to the invention, in particular an IPS or FFS display, particularly preferably a FFS or SG-FFS display.

The invention furthermore relates to a liquid-crystal display of the IPS or FFS type comprising a liquid-crystal cell comprising two substrates, where at least one substrate is transparent to light and at least one substrate has an electrode layer, and a layer, located between the substrates, of a liquid-crystalline medium comprising a polymerized component and a low-molecular-weight component, where the polymerized component is obtainable by polymerization of one or more polymerizable compounds in the liquid-crystalline medium between the substrates of the liquid-crystal cell, preferably with application of an electrical voltage, and where the low-molecular-weight component is a liquid-crystal mixture according to the invention as described above and below.

The displays in accordance with the present invention are preferably addressed by an active matrix (active matrix LCDs, AMDs for short), preferably by a matrix of thin-film transistors (TFTs). However, the liquid crystals according to the invention can also be used in an advantageous manner in displays having other known addressing means.

The invention furthermore relates to a process for the preparation of a liquid-crystalline medium according to the invention by mixing one or more compounds of formula I, preferably selected from the group of compounds of formulae I-1 to I-4, with one or more low-molecular-weight liquid-crystalline compounds, or a liquid-crystal mixture and optionally with further liquid-crystalline compounds and/or additives.

The following meanings apply above and below:

The term “FFS” is, unless indicated otherwise, used to represent FFS and SG-FFS displays.

The term “mesogenic group” is known to the person skilled in the art and is described in the literature, and denotes a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystalline (LC) phase in low-molecular-weight or polymeric substances. Compounds containing mesogenic groups (mesogenic compounds) do not necessarily have to have a liquid-crystalline phase themselves. It is also possible for mesogenic compounds to exhibit liquid-crystalline phase behavior only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units. An overview of the terms and definitions used in connection with mesogenic or liquid-crystalline compounds is given in Pure Appl. Chem. 73(5), 888 (2001) and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

The term “spacer group” or “spacer” for short, also referred to as “Sp” above and below, is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 73(5), 888 (2001) and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. Unless indicated otherwise, the term “spacer group” or “spacer” above and below denotes a flexible group which connects the mesogenic group and the polymerizable group(s) to one another in a polymerizable mesogenic compound.

For the purposes of this invention, the term “liquid-crystalline medium” is intended to denote a medium which comprises a liquid-crystal mixture and one or more polymerizable compounds (such as, for example, reactive mesogens). The term “liquid-crystal mixture” (or “host mixture”) is intended to denote a liquid-crystalline mixture which consists exclusively of unpolymerizable, low-molecular-weight compounds, preferably of two or more liquid-crystalline compounds and optionally further additives, such as, for example, chiral dopants or stabilizers.

Particular preference is given to liquid-crystal mixtures and liquid-crystalline media which have a nematic phase, in particular at room temperature.

In a preferred embodiment of the present invention, the liquid-crystal medium comprises one or more dielectrically positive compounds having a dielectric anisotropy of greater than 3, selected from the group of the compounds of the formulae II-1 and II-2:

n which the parameters have the respective meanings indicated above under formula II, and L²³ and L²⁴, independently of one another, denote H or F, preferably L²³ denotes F, and

has one of the meanings given for

and, in the case of formulae II-1 and II-2, X² preferably denotes F or OCF₃, particularly preferably F, and, in the case of formula II-2,

independently of one another, preferably denote

and/or selected from the group of the compounds of the formulae III-1 and III-2:

in which the parameters have the meanings given under formula III, and the media in accordance with the present invention may comprise, alternatively or in addition to the compounds of the formulae III-1 and/or III-2, one or more compounds of the formula III-3

in which the parameters have the respective meanings indicated above, and the parameters L³¹ and L³², independently of one another and of the other parameters, denote H or F.

The liquid-crystal medium preferably comprises compounds selected from the group of the compounds of the formulae II-1 and II-2 in which L²¹ and L²² and/or L²³ and L²⁴ both denote F.

In a preferred embodiment, the liquid-crystal medium comprises compounds selected from the group of the compounds of the formulae II-1 and II-2 in which L²¹, L²², L²³ and L²⁴ all denote F.

The liquid-crystal medium preferably comprises one or more compounds of the formula II-1. The compounds of the formula II-1 are preferably selected from the group of the compounds of the formulae II-1a to II-1e, preferably one or more compounds of formulae II-1a and/or II-1 b and/or II-1d, preferably of formula II-1a and/or II-1d or II-1b and/or II-1d, most preferably of formula II-1d:

in which the parameters have the respective meanings indicated above, and L²⁵ and L²⁶, independently of one another and of the other parameters, denote H or F, and preferably in the formulae II-1a and II-1b, L²¹ and L²² both denote F, in the formulae II-1c and II-1d, L²¹ and L²² both denote F and/or L²³ and L²⁴ both denote F, and in formula II-1e, L²¹, L²² and L²³ denote F.

The liquid-crystal medium preferably comprises one or more compounds of the formula II-2, which are preferably selected from the group of the compounds of the formulae II-2a to II-2k, preferably one or more compounds each of formulae II-2a and/or II-2h and/or II-2j:

in which the parameters have the respective meanings indicated above, and L²⁵ to L²⁸, independently of one another, denote H or F, preferably L²⁷ and L²⁸ both denote H, particularly preferably L²⁶ denotes H.

The liquid-crystal medium preferably comprises compounds selected from the group of the compounds of the formulae II-2a to II-2k in which L²¹ and L²² both denote F and/or L²³ and L²⁴ both denote F.

In a preferred embodiment, the liquid-crystal medium comprises compounds selected from the group of the compounds of the formulae II-2a to II-2k in which L²¹, L²², L²³ and L²⁴ all denote F.

Especially preferred compounds of the formula II-2 are the compounds of the following formulae, particularly preferred of formulae II-2a-1 and/or II-2h-1 and/or II-2k-2:

in which R² and X² have the meanings indicated above, and X² preferably denotes F.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1. The compounds of the formula III-1 are preferably selected from the group of the compounds of the formulae III-1a to III-1j, preferably from formulae III-1c, III-1f, III-1g and III-1j:

in which the parameters have the meanings given above and preferably in which the parameters have the respective meanings indicated above, the parameters L³³ and L³⁴, independently of one another and of the other parameters, denote H or F, and the parameters L³⁵ and L³⁶, independently of one another and of the other parameters, denote H or F.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1c, which are preferably selected from the group of the compounds of the formulae III-1c-1 to III-1c-5, preferably of formulae III-1c-1 and/or III-1c-2, most preferably of formula III-1c-1:

in which R³ has the meaning indicated above.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1f, which are preferably selected from the group of the compounds of the formulae III-1f-1 to III-1f-6, preferably of formulae III-1f-1 and/or III-1f-2 and/or III-1f-3 and/or III-1f-6, more preferably of formula III-1f-3 and/or III-1f-6, more preferably of formula III-1f-6:

in which R³ has the meaning indicated above.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1g, which are preferably selected from the group of the compounds of the formulae III-1g-1 to III-1g-5, preferably of formula III-1 g-3:

in which R³ has the meaning indicated above.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1 h, which are preferably selected from the group of the compounds of the formulae III-1 h-1 to III-1 h-3, preferably of the formula III-1 h-3:

in which the parameters have the meanings given above, and X³ preferably denotes F.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1j, which are preferably selected from the group of the compounds of the formulae III-1i-1 and III-1i-2, preferably of the formula III-1i-2:

in which the parameters have the meanings given above, and X³ preferably denotes F.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-1j, which are preferably selected from the group of the compounds of the formulae III-1j-1 and III-1j-2, preferably of the formula III-1j-1:

in which the parameters have the meanings given above.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-2. The compounds of the formula III-2 are preferably selected from the group of the compounds of the formulae III-2a and III-2b, preferably of formula III-2b:

in which the parameters have the respective meanings indicated above, and the parameters L³³ and L³⁴, independently of one another and of the other parameters, denote H or F.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-2a, which are preferably selected from the group of the compounds of the formulae III-2a-1 to III-2a-6:

in which R³ has the meaning indicated above.

The liquid-crystal medium preferably comprises one or more compounds of the formula III-2b, which are preferably selected from the group of the compounds of the formulae III-2b-1 to III-2b-4, preferably III-2b-4:

in which R³ has the meaning indicated above.

Alternatively or in addition to the compounds of the formulae III-1 and/or III-2, the media in accordance with the present invention may comprise one or more compounds of the formula III-3

in which the parameters have the respective meanings indicated above under formula III.

These compounds are preferably selected from the group of the formulae III-3a and III-3b:

in which R³ has the meaning indicated above.

The liquid-crystalline media in accordance with the present invention preferably comprise one or more dielectrically neutral compounds having a dielectric anisotropy in the range from −1.5 to 3, preferably selected from the group of the compounds of the formulae VI, VII, VIII and IX.

In the present application, the elements all include their respective isotopes. In particular, one or more H in the compounds may be replaced by D, and this is also particularly preferred in some embodiments. A correspondingly high degree of deuteration of the corresponding compounds enables, for example, detection and recognition of the compounds. This is very helpful in some cases, in particular in the case of the compounds of formula I.

In the present application,

-   alkyl particularly preferably denotes straight-chain alkyl, in     particular CH₃—, C₂H₅—, n-C₃H₇—, n-C₄H₉— or n-C₅H₁₁—, and -   alkenyl particularly preferably denotes CH₂═CH—, E-CH₃—CH═CH—,     CH₂═CH—CH₂—CH₂—, E-CH₃—CH═CH—CH₂—CH₂— or E-(n-C₃H₇)—CH═CH—.

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VI selected from the group of the compounds of the formulae VI-1 and VI-2, preferably one or more compounds each of formulae VI-1 and one or more compounds of formula VI-2,

in which the parameters have the respective meanings given above under formula VI, and preferably in formula VI-1

-   R⁶¹ and R⁶² independently of each other denote methoxy, ethoxy,     propoxy, butoxy (also or pentoxy, preferably ethoxy, butoxy or     pentoxy, more preferably ethoxy or butoxy and, most preferably     butoxy.     in formula VI-2 -   R⁶¹ preferably denotes vinyl, 1-E-propenyl, but-4-en-1-yl,     pent-1-en-1-yl or pent-3-en-1-yl and n-propyl or n-pentyl and -   R⁶² denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably having 2 to 5 C atoms, or, preferably, an unsubstituted     alkoxy radical having 1 to 6 C atoms, particularly preferably having     2 or 4 C atoms and, most preferably, ethoxy, and

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VII selected from the group of the compounds of the formulae VII-1 to VII-3, preferably one or more compounds each of the formulae VII-1 and one or more compounds of formula VII-2,

in which the parameters have the respective meanings given above under formula VII, and preferably

-   R⁷¹ denotes vinyl, 1-E-propenyl, but-4-en-1-yl, pent-1-en-1-yl or     pent-3-en-1-yl, n-propyl or n-pentyl and -   R⁷² denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably having 2 to 5 C atoms, or, preferably, an unsubstituted     alkoxy radical having 1 to 6 C atoms, particularly preferably having     2 or 4 C atoms and, most preferably, ethoxy.

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VI-1 selected from the group of the following compounds:

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VI-2 selected from the group of the following compounds:

In a preferred embodiment of the present invention, the media according

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VII-1 selected from the group of the following compounds:

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VII-2 selected from the group of the following compounds:

In addition to the compounds of formula I or the preferred sub-formulae thereof, the media in accordance with the present invention preferably comprise one or more dielectrically negative compounds selected from the group of compounds of the formulae VI and VII preferably in a total concentration in the range from 5% or more to 90% or less, preferably from 10% or more to 80% or less, particularly preferably from 20% or more to 70% or less, based on the medium as a whole.

In a preferred embodiment of the present invention, the media according to the invention in each case comprise one or more compounds of formula VIII selected from the group of the compounds of the formulae VIII-1 to VIII-3, preferably one or more compounds each of the formulae VIII-1 and/or one or more compounds of formula VIII-3,

in which the parameters have the respective meanings given above under formula VIII, and preferably

-   R⁸¹ denotes vinyl, 1-E-propenyl, but-4-en-1-yl, pent-1-en-1-yl or     pent-3-en-1-yl, ethyl, n-propyl or n-pentyl, alkyl, preferably     ethyl, n-propyl or n-pentyl and -   R⁸² denotes an unsubstituted alkyl radical having 1 to 7 C atoms,     preferably having 1 to 5 C atoms or an unsubstituted alkoxy radical     having 1 to 6 C atoms.

In formulae VIII-1 and VIII-2 R⁸² preferably denotes alkoxy having 2 or 4 C atoms and, most preferably, ethoxy, and in formula VIII-3 R⁸² preferably denotes preferably alkyl, preferably methyl, ethyl or n-propyl, most preferably methyl.

In a further preferred embodiment, the medium comprises one or more compounds of formula IV

in which

-   R⁴¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms or     an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably     an n-alkyl radical, particularly preferably having 2, 3, 4 or 5 C     atoms, and -   R⁴² denotes an unsubstituted alkyl radical having 1 to 7 C atoms, an     unsubstituted alkenyl radical having 2 to 7 C atoms, or an     unsubstituted alkoxy radical having 1 to 6 C atoms, both preferably     having 2 to 5 C atoms, an unsubstituted alkenyl radical preferably     having 2, 3 or 4 C atoms, more preferably a vinyl radical or     1-propenyl radical and in particular a vinyl radical.

In a particularly preferred embodiment, the medium comprises one or more compounds of formula IV selected from the group of the compounds of the formulae IV-1 to IV-4, preferably of formula IV-1,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having     1 to 7 C atoms, preferably having 2 to 5 C atoms, -   alkenyl and alkenyl′, independently of one another, denote an     alkenyl radical having 2 to 5 C atoms, preferably having 2 to 4 C     atoms, particularly preferably 2 C atoms, -   alkenyl′ denotes an alkenyl radical having 2 to 5 C atoms,     preferably having 2 to 4 C atoms, particularly preferably having 2     to 3 C atoms, and -   alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to     4 C atoms.

In a particularly preferred embodiment, the media according to the invention comprise one or more compounds of formula IV-1 and/or one or more compounds of formula IV-2.

In a further preferred embodiment, the medium comprises one or more compounds of formula V.

The media according to the invention preferably comprise the following compounds in the total concentrations indicated, based on the medium as a whole:

-   -   1-60% by weight of one or more compounds selected from the group         of the compounds of formula I and     -   5-60% by weight of one or more compounds of formula II,         preferably selected from the group of the compounds of the         formulae II-1 and II-2 and/or     -   5-25% by weight of one or more compounds of formula III, and/or     -   5-45% by weight of one or more compounds of formula IV and/or     -   5-25% by weight of one or more compounds of formula V, and/or     -   5-25% by weight of one or more compounds of formula VI, and/or     -   5-20% by weight of one or more compounds of formula VII, and/or     -   5-30% by weight of one or more compounds of formula VIII,         preferably selected from the group of the compounds of the         formulae VIII-1 and VIII-2 and/or     -   0-60% by weight of one or more compounds of formula IX,     -   where the total content of all compounds of formulae I-IX which         are present in the medium preferably is 95% or more and, more         preferably 100%.

The latter condition holds for all media according to the present application.

In a further preferred embodiment, the media in accordance with the present invention in addition to the compounds of formula I or the preferred sub-formulae thereof, and to the compounds of formulae VI and/or VII and/or VIII and/or IX, preferably comprise one or more dielectrically neutral compounds selected from the group of compounds of formulae IV and V preferably in a total concentration in the range from 5% or more to 90% or less, preferably from 10% or more to 80% or less, particularly preferably from 20% or more to 70% or less, based on the medium as a whole.

The medium according to the invention in a particularly preferred embodiment comprises, based on the medium as a whole:

-   -   one or more compounds of formula II in a total concentration in         the range from 5% or more to 50% or less, preferably in the         range from 10% or more to 40% or less, and/or     -   one or more compounds of formula VII-1 in a total concentration         in the range from 5% or more to 30% or less, and/or     -   one or more compounds of formula VII-2 in a total concentration         in the range from 3% or more to 30% or less.

Preferably the concentration of the compounds of formula I in the media according to the invention is in the range from 1% or more to 60% or less, more preferably from 5% or more to 40% or less, most preferably from 8% or more to 35% or less, based on the medium as a whole.

In a preferred embodiment of the present invention the concentration of the compounds of formula II in the media is in the range from 3% or more to 60% or less, more preferably from 5% or more to 55% or less, more preferably from 10% or more to 50% or less and, most preferably, from 15% or more to 45% or less, based on the medium as a whole.

In a preferred embodiment of the present invention the concentration of the compounds of formula VII in the media is in the range from 2% or more to 50% or less, more preferably from 5% or more to 40% or less, more preferably from 10% or more to 35% or less and, most preferably, from 15% or more to 30% or less, based on the medium as a whole.

In a preferred embodiment of the present invention the concentration of the compounds of formula VII-1 in the media is in the range from 1% or more to 40% or less, more preferably either from 2% or more to 35% or less, or, alternatively, from 15% or more to 25% or less, based on the medium as a whole.

In a preferred embodiment of the present invention the concentration of the compounds of formula VII-2 in the media, if present, is in the range from 1% or more to 40% or less, more preferably from 5% or more to 35% or less and, most preferably, from 10% or more to 30% or less, based on the medium as a whole.

The present invention also relates to electro-optical displays or electro-optical components which contain liquid-crystalline media according to the invention. Preference is given to electro-optical displays which are based on the VA, ECB, IPS or FFS effect, preferably on the VA; IPS or FFS effect, and in particular those which are addressed by means of an active-matrix addressing device.

Accordingly, the present invention likewise relates to the use of a liquid-crystalline medium according to the invention in an electro-optical display or in an electro-optical component, and to a process for the preparation of the liquid-crystalline media according to the invention, characterized in that one or more compounds of formula I are mixed with one or more compounds of formula II, preferably with one or more compounds of the sub-formulae II-1 and/or II-2 and/or with one or more compounds of formula VII, preferably with one or more compounds of the sub-formulae VII-1 and/or VII-2, particularly preferably one or more compounds from two or more, preferably from three or more, different formulae thereof and very particularly preferably from all four of these formulae II-1, II-2, VII-1 and VII-2 and one or more further compounds, preferably selected from the group of the compounds of the formulae IV and V, more preferably with one or more compounds both of formula IV and of formula V.

In a further preferred embodiment, the medium comprises one or more compounds of formula IV, selected from the group of the compounds of the formulae IV-2 and IV-3,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having     1 to 7 C atoms, preferably having 2 to 5 C atoms, -   alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to     4 C atoms.

In a further preferred embodiment, the medium comprises one or more compounds of formula V selected from the group of the compounds of the formulae V-1 and V-2, preferably of formulae V-1,

in which the parameters have the meanings given above under formula V, and preferably

-   R⁵¹ denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C     atoms, and -   R⁵² denotes alkyl having 1 to 7 C atoms, alkenyl having 2 to 7 C     atoms or alkoxy having 1 to 6 C atoms, preferably alkyl or alkenyl,     particularly preferably alkyl.

In a further preferred embodiment, the medium comprises one or more compounds of formula V-1 selected from the group of the compounds of the formulae V-1a and V-1b,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having     1 to 7 C atoms, preferably having 2 to 5 C atoms, and -   alkenyl denotes alkenyl having 2 to 7 C atoms, preferably having 2     to 5 C atoms.

In addition, the present invention relates to a method for the reduction of the wavelength dispersion of the birefringence of a liquid-crystalline medium which comprises one or more compounds of formula II, optionally one or more compounds selected from the group of the compounds of the formulae VII-1 and VII-2 and/or one or more compounds of formula IV and/or one or more compounds of formula V, characterized in that one or more compounds of formula I are used in the medium.

Besides compounds of the formulae I to V, other constituents may also be present, for example in an amount of up to 45%, but preferably up to 35%, in particular up to 10%, of the mixture as a whole.

The media according to the invention may optionally also comprise a dielectrically positive component, whose total concentration is preferably 20% or less, more preferably 10% or less, based on the entire medium.

In a preferred embodiment, the liquid-crystal media according to the invention comprise in total, based on the mixture as a whole,

1% or more to 20% or less, preferably 2% or more to 15% or less, particularly preferably 3% or more to 12% or less, of the compound of formula I. 20% or more to 50% or less, preferably 25% or more to 45% or less, particularly preferably 30% or more to 40% or less, of compounds of formulae II and/or III, and 0% or more to 35% or less, preferably 2% or more to 30% or less, particularly preferably 3% or more to 25% or less, of compounds of formulae IV and/or V, and 5% or more to 50% or less 10% or more to 45% or less, preferably 15% or more to 40% or less of compounds of the formulae VI and/or VII and/or VIII and/or IX.

The liquid-crystal media in accordance with the present invention may comprise one or more chiral compounds.

Particularly preferred embodiments of the present invention meet one or more of the following conditions,

where the acronyms (abbreviations) are explained in Tables A to C and illustrated by examples in Table D.

Preferably the media according to the present invention fulfil one or more of the following conditions (percentages are based on the medium as a whole).

-   i. The liquid-crystalline medium has a birefringence of 0.060 or     more, particularly preferably 0.070 or more. -   ii. The liquid-crystalline medium has a birefringence of 0.200 or     less, particularly preferably 0.180 or less. -   iii. The liquid-crystalline medium has a birefringence in the range     from 0.090 or more to 0.120 or less. -   iv. The liquid-crystalline medium comprises one or more particularly     preferred compounds of formula I-1. -   v. The total concentration of the compounds of formula II in the     mixture as a whole is 25% or more, preferably 30% or more, and is     preferably in the range from 25% or more to 49% or less,     particularly preferably in the range from 29% or more to 47% or     less, and very particularly preferably in the range from 37% or more     to 44% or less. -   vi. The liquid-crystalline medium comprises one or more compounds of     formula IV selected from the group of the compounds of the following     formulae: CC-n-V and/or CC-n-Vm and/or CC-V-V and/or CC-V-Vn and/or     CC-nV-Vn, particularly preferably CC-3-V, preferably in a     concentration of up to 60% or less, particularly preferably up to     50% or less, and optionally additionally CC-3-V1, preferably in a     concentration of up to 15% or less, and/or CC-4-V, preferably in a     concentration of up to 24% or less, particularly preferably up to     30% or less. -   vii. The media comprise the compound of formula CC-n-V, preferably     CC-3-V, preferably in a concentration of 1% or more to 60% or less,     more preferably in a concentration of 3% or more to 35% or less. -   viii. The total concentration of the compounds of formula CC-3-V in     the mixture as a whole preferably either is 15% or less, preferably     10% or less or 20% or more, preferably 25% or more. -   ix. The total concentration of the compounds of formula Y-nO-Om in     the mixture as a whole is 2% or more to 30% or less, preferably 5%     or more to 15% or less. -   x. The total concentration of the compounds of formula CY-n-Om in     the mixture as a whole is 5% or more to 60% or less, preferably 15%     or more to 45% or less. -   xi. The total concentration of the compounds of formula CCY-n-Om     and/or CCY-n-m, preferably of CCY-n-Om, in the mixture as a whole is     5% or more to 40% or less, preferably 1% or more to 25% or less. -   xii. The total concentration of the compounds of formula CLY-n-Om in     the mixture as a whole is 5% or more to 40% or less, preferably 10%     or more to 30% or less. -   xiii. The liquid-crystalline medium comprises one or more compounds     of formula IV, preferably of the formulae IV-1 and/or IV-2,     preferably in a total concentration of 1% or more, in particular 2%     or more, and very particularly preferably 3% or more to 50% or less,     preferably 35% or less. -   xiv. The liquid-crystalline medium comprises one or more compounds     of formula V, preferably of the formulae V-1 and/or V-2, preferably     in a total concentration of 1% or more, in particular 2% or more,     and very particularly preferably 15% or more to 35% or less,     preferably to 30% or less. -   xv. The total concentration of the compounds of formula CCP-V-n,     preferably CCP-V-1, in the mixture as a whole preferably is 5% or     more to 30% or less, preferably 15% or more to 25% or less. -   xvi. The total concentration of the compounds of formula CCP-V2-n,     preferably CCP-V2-1, in the mixture as a whole preferably is 1% or     more to 15% or less, preferably 2% or more to 10% or less.

The invention furthermore relates to an electro-optical display having active-matrix addressing based on the VA, ECB, IPS, FFS or UB-FFS effect, characterized in that it contains, as dielectric, a liquid-crystalline medium in accordance with the present invention.

The liquid-crystal mixture preferably has a nematic phase range having a width of at least 70 degrees.

The rotational viscosity γ₁ is preferably 350 mPa·s or less, preferably 250 mPa·s or less and, in particular, 150 mPa·s or less.

The mixtures according to the invention are suitable for all IPS and FFS-TFT applications using dielectrically positive liquid crystalline media, such as, e.g. SG-FFS.

The liquid-crystalline media according to the invention preferably virtually completely consist of 4 to 15, in particular 5 to 12, and particularly preferably 10 or less, compounds. These are preferably selected from the group of the compounds of the formula I, II III, IV, V, VI, VII, VIII and IX.

The liquid-crystalline media according to the invention may optionally also comprise more than 18 compounds. In this case, they preferably comprise 18 to 25 compounds.

In a preferred embodiment, the liquid-crystal media according to the invention predominantly comprise, preferably consist essentially of and, most preferably, virtually completely consist of compounds, which do not comprise a cyano group.

In a preferred embodiment, the liquid-crystal media according to the invention comprise compounds selected from the group of the compounds of the formulae I, II, and III, IV and V and VI to IX, preferably selected from the group of the compounds of the formulae I-1, I-2, I-3, I-4, II-1, II-2, III-1, III-2, IV, V, VII-1, VII-2, VIII and IX; they preferably predominantly comprise, particularly preferably consist essentially of, and very particularly preferably virtually completely consist of the compounds of the said formulae.

The liquid-crystal media according to the invention preferably have a nematic phase from in each case at least −10° C. or less to 70° C. or more, particularly preferably from −20° C. or less to 80° C. or more, very particularly preferably from −30° C. or less to 85° C. or more and most preferably from −40° C. or less to 90° C. or more.

The expression “have a nematic phase” here means, on the one hand, that no smectic phase and no crystallization are observed at low temperatures at the corresponding temperature and, on the other hand, that no clearing occurs on heating out of the nematic phase. The investigation at low temperatures is carried out in a flow viscometer at the corresponding temperature and checked by storage in test cells having a cell thickness corresponding to the electro-optical application for at least 100 hours. If the storage stability at a temperature of −20° C. in a corresponding test cell is 1000 h or more, the medium is regarded as stable at this temperature. At temperatures of −30° C. and −40° C., the corresponding times are 500 h and 250 h respectively. At high temperatures, the clearing point is measured in capillaries by conventional methods.

In a preferred embodiment, the liquid-crystal media according to the invention are characterized by optical anisotropy values in the moderate to low range. The birefringence values are preferably in the range from 0.075 or more to 0.130 or less, particularly preferably in the range from 0.085 or more to 0.120 or less and very particularly preferably in the range from 0.090 or more to 0.115 or less.

In this embodiment, the liquid-crystal media according to the invention have a positive dielectric anisotropy and relatively high absolute values of the dielectric anisotropy Ac, which preferably is in the range from 0.5 or more, preferably of 1.0 or more, more preferably of 2.0 or more to 20 or less, more preferably to 15 or less, more preferably from 3.0 or more to 10 or less, particularly preferably from 4.0 or more to 9.0 or less and very particularly preferably from 4.5 or more to 8.0 or less.

The liquid-crystal media according to the invention preferably have relatively low values for the threshold voltage (V₀) in the range from 1.0 V or more to 2.5 V or less, preferably from 1.2 V or more to 2.2 V or less, particularly preferably from 1.3 V or more to 2.0 V or less.

In a further preferred embodiment, the liquid-crystal media according to the invention preferably have relatively high values of the average dielectric constant (∈_(av.)≡(∈_(∥)+2∈_(⊥))/3) which are preferably in the range from 8.0 or more to 25.0 or less, preferably from 8.5 or more to 20.0 or less, still more preferably from 9.0 or more to 19.07 or less, particularly preferably from 10.0 or more to 18.0 or less and very particularly preferably from 11.0 or more to 16.5 or less.

In addition, the liquid-crystal media according to the invention have high values for the VHR in liquid-crystal cells.

In freshly filled cells at 20° C. in the cells, these VHR are greater than or equal to 95%, preferably greater than or equal to 97%, particularly preferably greater than or equal to 98% and very particularly preferably greater than or equal to 99%, and after 5 minutes in the oven at 100° C. in the cells, these are greater than or equal to 90%, preferably greater than or equal to 93%, particularly preferably greater than or equal to 96% and very particularly preferably greater than or equal to 98%.

In general, liquid-crystal media having a low addressing voltage or threshold voltage here have a lower VHR than those having a higher addressing voltage or threshold voltage, and vice versa.

These preferred values for the individual physical properties are preferably also in each case maintained by the media according to the invention in combination with one another.

In the present application, the term “compounds”, also written as “compound(s)”, means both one and also a plurality of compounds, unless explicitly indicated otherwise.

In a preferred embodiment, the liquid-crystalline media according to the invention comprise:

one or more compounds of formula I and one or more compounds of formula II, preferably of the formulae PUQU-n-F, CDUQU-n-F, APUQU-n-F and PGUQU-n-F (defined below), and/or one or more compounds of formula III, preferably of the formulae CCP-n-OT, CGG-n-F, and CGG-n-OD (defined below), and/or one or more compounds of formulae IV and/or V, preferably of the formulae CC-n-V, CCP-n-m, CCP-V-n, CCP-V2-n and CGP-n-n (defined below), and/or one or more compounds of formula VI, preferably of the formulae Y-n-Om, Y-nO-Om and/or CY-n-Om (defined below), especially selected from the group of the compounds of the formulae Y-3-O1, Y-4O-O4, CY-3-O2, CY-3-O4, CY-5-O2 and CY-5-O4 (defined below), and/or optionally, preferably obligatorily, one or more compounds of formula VII-1, preferably selected from the group of the compounds of the formulae CCY-n-m and CCY-n-Om (defined below), preferably of formula CCY-n-Om, preferably selected from the group of the compounds of the formulae CCY-3-O2, CCY-2-O2, CCY-3-O1, CCY-3-O3, CCY-4-O2, CCY-3-O2 and CCY-5-O2 (defined below), and/or optionally, preferably obligatorily, one or more compounds of formula VII-2, preferably of formula CLY-n-Om (defined below), preferably selected from the group of the compounds of the formulae CLY-2-O4, CLY-3-O2, CLY-3-O3 (defined below), and/or one or more compounds of formula VIII, preferably of the formulae CZY-nO-n and CCOY-n-m (defined below), and/or one or more compounds of formula IX, preferably of the formula PYP-n-m (defined below), and/or optionally, preferably obligatorily, one or more compounds of formula IV, preferably selected from the group of the compounds of the formulae CC-n-V, CC-n-Vm and CC-nV-Vm, preferably CC-3-V, CC-3-V1, CC-4-V, CC-5-V and CC-V-V (defined below), particularly preferably selected from the group of the compounds CC-3-V, CC-3-V1, CC-4-V and CC-V-V, very particularly preferably the compound CC-3-V, and optionally additionally the compound(s) CC-4-V and/or CC-3-V1 and/or CC-V-V, and/or optionally, preferably obligatorily, one or more compounds of formula V, preferably of the formulae CCP-V-1 and/or CCP-V2-1 (defined below).

In a specific preferred embodiment of the present invention, the media according to the invention comprise one or more compounds of formula IX,

The compounds of formula IX, are also highly suitable as stabilizers in liquid-crystal mixtures, especially in case p=q=1 and ring A⁹=1,4-phenylene. In particular, they stabilize the VHR of the mixtures against UV exposure.

In a preferred embodiment the media according to the invention comprise one or more compounds of formula IX selected from one or more formulae of the group of the compounds of the formulae IX-1 to IX-4, very particularly preferably of the formulae IX-1 to IX-3,

in which the parameters have the meanings given under formula IX.

In a further preferred embodiment, the medium comprises one or more compounds of formula IX-3, preferably of formula IX-3-a,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having     1 to 7 C atoms, preferably having 2 to 5 C atoms.

In case the compounds of formula IX are used in the liquid crystalline media according to the present application, they are preferably present in a concentration of 20% or less, more preferably of 10% or less and, most preferably, of 5% or less, based on the medium as a whole, and for the individual i.e. (homologous) compounds preferably in a concentration of 10% or less and, more preferably, of 5% or less, based on the medium as a whole.

For the present invention, the following definitions apply in connection with the specification of the constituents of the compositions, unless indicated otherwise in individual cases:

-   -   “comprise”: the concentration of the constituents in question in         the composition is preferably 5% or more, particularly         preferably 10% or more, very particularly preferably 20% or         more,     -   “predominantly consist of”: the concentration of the         constituents in question in the composition is preferably 50% or         more, particularly preferably 55% or more and very particularly         preferably 60% or more,     -   “essentially consist of”: the concentration of the constituents         in question in the composition is preferably 80% or more,         particularly preferably 90% or more and very particularly         preferably 95% or more, and     -   “virtually completely consist of”: the concentration of the         constituents in question in the composition is preferably 98% or         more, particularly preferably 99% or more and very particularly         preferably 100.0%.

This applies both to the media as compositions with their constituents, which can be components and compounds, and also to the components with their constituents, the compounds. Only in relation to the concentration of an individual compound relative to the medium as a whole does the term comprise mean: the concentration of the compound in question is preferably 1% or more, particularly preferably 2% or more, very particularly preferably 4% or more.

For the present invention, “≦” means less than or equal to, preferably less than, and “≧” means greater than or equal to, preferably greater than.

For the present invention,

denote trans-1,4-cyclohexylene, and

denote 1,4-phenylene.

For the present invention, the expression “dielectrically positive compounds” means compounds having a Δ∈ of >1.5, the expression “dielectrically neutral compounds” means those where −1.5≦Δ∈≦1.5 and the expression “dielectrically negative compounds” means those where Δ∈<−1.5. The dielectric anisotropy of the compounds is determined here by dissolving 10% of the compounds in a liquid-crystalline host and determining the capacitance of the resultant mixture in each case in at least one test cell having a cell thickness of 20 μm with homeotropic and with homogeneous surface alignment at 1 kHz. The measurement voltage is typically 0.5 V to 1.0 V, but is always lower than the capacitive threshold of the respective liquid-crystal mixture investigated.

The host mixture used for dielectrically positive and dielectrically neutral compounds is ZLI-4792 and that used for dielectrically negative compounds is ZLI-2857, both from Merck KGaA, Germany. The values for the respective compounds to be investigated are obtained from the change in the dielectric constant of the host mixture after addition of the compound to be investigated and extrapolation to 100% of the compound employed. The compound to be investigated is dissolved in the host mixture in an amount of 10%. If the solubility of the substance is too low for this purpose, the concentration is halved in steps until the investigation can be carried out at the desired temperature.

The liquid-crystal media according to the invention may, if necessary, also comprise further additives, such as, for example, stabilizers and/or pleo-chroitic, e.g. dichroitic, dyes and/or chiral dopants in the usual amounts. The amount of these additives employed is preferably in total 0% or more to 10% or less, based on the amount of the entire mixture, particularly preferably 0.1% or more to 6% or less. The concentration of the individual compounds employed is preferably 0.1% or more to 3% or less. The concentration of these and similar additives is generally not taken into account when specifying the concentrations and concentration ranges of the liquid-crystal compounds in the liquid-crystal media.

In a preferred embodiment, the liquid-crystal media according to the invention comprise a polymer precursor which comprises one or more reactive compounds, preferably reactive mesogens, and, if necessary, also further additives, such as, for example, polymerization initiators and/or polymerization moderators, in the usual amounts. The amount of these additives employed is in total 0% or more to 10% or less, based on the amount of the entire mixture, preferably 0.1% or more to 2% or less. The concentration of these and similar additives is not taken into account when specifying the concentrations and concentration ranges of the liquid-crystal compounds in the liquid-crystal media.

The compositions consist of a plurality of compounds, preferably 3 or more to 30 or fewer, particularly preferably 6 or more to 20 or fewer and very particularly preferably 10 or more to 16 or fewer compounds, which are mixed in a conventional manner. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent of the mixture. This is advantageously carried out at elevated temperature. If the selected temperature is above the clearing point of the principal constituent, completion of the dissolution operation is particularly easy to observe. However, it is also possible to prepare the liquid-crystal mixtures in other conventional ways, for example using pre-mixes or from a so-called “multi-bottle system”.

The mixtures according to the invention exhibit very broad nematic phase ranges having clearing points of 65° C. or more, very favorable values for the capacitive threshold, relatively high values for the holding ratio and at the same time very good low-temperature stabilities at −30° C. and −40° C. Furthermore, the mixtures according to the invention are distinguished by low rotational viscosities γ₁.

It goes without saying to the person skilled in the art that the media according to the invention for use in VA, IPS, FFS or PALC displays may also comprise compounds in which, for example, H, N, O, Cl, F have been replaced by the corresponding isotopes.

The structure of the liquid-crystal displays according to the invention corresponds to the usual geometry, as described, for example, in EP-A 0 240 379.

The liquid-crystal phases according to the invention can be modified by means of suitable additives in such a way that they can be employed in any type of, for example, IPS and FFS LCD display that has been disclosed to date.

Table E below indicates possible dopants which can be added to the mixtures according to the invention. If the mixtures comprise one or more dopants, it is (they are) employed in amounts of 0.01% to 4%, preferably 0.1% to 1.0%.

Stabilizers which can be added, for example, to the mixtures according to the invention, preferably in amounts of 0.01% to 6%, in particular 0.1% to 3%, are shown below in Table F.

For the purposes of the present invention, all concentrations are, unless explicitly noted otherwise, indicated in percent by weight and relate to the corresponding mixture as a whole or to the respective mixture component, again as a whole, unless explicitly indicated otherwise. In this context the term “mixture” describes the liquid crystalline medium.

All temperature values indicated in the present application, such as, for example, the melting point T(C,N), the smectic (S) to nematic (N) phase transition T(S,N) and the clearing point T(N,I), are indicated in degrees Celsius (° C.) and all temperature differences are correspondingly indicated in differential degrees (° or degrees), unless explicitly indicated otherwise.

For the present invention, the term “threshold voltage” relates to the capacitive threshold (V₀), also known as the Freedericks threshold, unless explicitly indicated otherwise.

All physical properties are and have been determined in accordance with “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, status November 1997, Merck KGaA, Germany, and apply for a temperature of 20° C., and Δn is determined at 436 nm, 589 nm and at 633 nm, and Δ∈ at 1 kHz, unless explicitly indicated otherwise in each case.

The electro-optical properties, for example the threshold voltage (V₀) (capacitive measurement), are, as is the switching behavior, determined in test cells produced at Merck Japan. The measurement cells have soda-lime glass substrates and are constructed in an ECB or VA configuration with polyimide alignment layers (SE-1211 with diluent **26 (mixing ratio 1:1), both from Nissan Chemicals, Japan), which have been rubbed perpendicularly to one another and effect homeotropic alignment of the liquid crystals. The surface area of the transparent, virtually square ITO electrodes is 1 cm².

Unless indicated otherwise, a chiral dopant is not added to the liquid-crystal mixtures used, but the latter are also particularly suitable for applications in which doping of this type is necessary.

The rotational viscosity is determined using the rotating permanent magnet method and the flow viscosity in a modified Ubbelohde viscometer. For liquid-crystal mixtures ZLI-2293, ZLI-4792 and MLC-6608, all products from Merck KGaA, Darmstadt, Germany, the rotational viscosity values determined at 20° C. are 161 mPa·s, 133 mPa·s and 186 mPa·s respectively, and the flow viscosity values (ν) are 21 mm²·s⁻¹, 14 mm²·s⁻¹ and 27 mm²·s⁻¹, respectively.

The dispersion of the materials may for practical purposes be conveniently characterized in the following way, which is used throughout this application unless explicitly stated otherwise. The values of the birefringence are determined at a temperature of 20° C. at several fixed wavelengths using a modified Abbé refractometer with homeotropically aligning surfaces on the sides of the prisms in contact with the material. The birefringence values are determined at the specific wavelength values of 436 nm (respective selected spectral line of a low pressure mercury lamp), 589 nm (sodium “D” line) and 633 nm (wavelength of a HE-Ne laser (used in combination with an attenuator/diffusor in order to prevent damage to the eyes of the observers. In the following table An is given at 589 nm and Δ(Δn) is given as Δ(Δn)=Δn(436 nm)−Δn(633 nm).

The following symbols are used, unless explicitly indicated otherwise:

-   V₀ threshold voltage, capacitive [V] at 20° C., -   n_(e) extraordinary refractive index measured at 20° C. and 589 nm, -   n_(o) ordinary refractive index measured at 20° C. and 589 nm, -   Δn optical anisotropy measured at 20° C. and 589 nm, -   λ wavelength λ [nm], -   Δn(λ) optical anisotropy measured at 20° C. and wavelength λ, -   Δ(Δn) change in optical anisotropy defined as: Δn(20° C., 436     nm)−Δn(20° C., 633 nm), -   Δ(Δn*) “relative change in optical anisotropy” defined as:     Δ(Δn)/Δn(20° C., 589 nm), -   ∈_(⊥) dielectric susceptibility perpendicular to the director at     20° C. and 1 kHz, -   ∈_(∥) dielectric susceptibility parallel to the director at 20° C.     and 1 kHz, -   Δ∈ dielectric anisotropy at 20° C. and 1 kHz, -   T(N,I) or cl.p.clearing point [° C.], -   ν flow viscosity measured at 20° C. [mm²·s⁻¹], -   γ₁ rotational viscosity measured at 20° C. [mPa·s], -   k₁₁ elastic constant, “splay” deformation at 20° C. [pN], -   k₂₂ elastic constant, “twist” deformation at 20° C. [pN], -   k₃₃ elastic constant, “bend” deformation at 20° C. [pN], -   LTS low-temperature stability of the phase, determined in test     cells, -   VHR voltage holding ratio, -   ΔVHR decrease in the voltage holding ratio, and -   S_(rel) relative stability of the VHR,

The following examples explain the present invention without limiting it. However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective concentrations thereof and combinations thereof with one another. In addition, the examples illustrate the properties and property combinations that are accessible.

For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated by means of acronyms, with the transformation into chemical formulae taking place in accordance with Tables A to C below. All radicals C_(n)H_(2n+1), C_(m)H_(2m+1) and C_(l)H_(2l+1) or C_(n)H_(2n), C_(m)H_(2m) and C_(l)H_(2l) are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and I C atoms respectively. Preferably n, m and I are independently of each other 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the nuclei of the compound, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left- and right-hand end groups of the molecules. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.

TABLE A Ring elements C

D

DI

A

AI

P

G

GI

U

UI

Y

P(F, Cl)Y

P(Cl,F)Y

np

n3f

nN3fI

th

thI

tH2f

tH2fI

o2f

o2fI

dh

B

K

KI

L

LI

F

FI

TABLE B Bridging units E —CH₂—CH₂— V —CH═CH— T —C≡C— W —CF₂—CF₂— B —CF═CF— Z —CO—O— ZI —O—CO— X —CF═CH— XI —CH═CF— O —CH₂—O— OI —O—CH₂— Q —CF₂—O— QI —O—CF₂—

TABLE C End groups On the left individually or in combination On the right individually or in combination -n- C_(n)H_(2n+1)— -n —C_(n)H_(2n+1) -nO- C_(n)H_(2n+1)—O— -nO —O—C_(n)H_(2n+1) -V- CH₂═CH— -V —CH═CH₂ -nV- C_(n)H_(2n+1)—CH═CH— -nV —C_(n)H_(2n)—CH═CH₂ -Vn- CH₂═CH—C_(n)H_(2n)— -Vn —CH═CH—C_(n)H_(2n+1) -nVm- C_(n)H_(2n+1)—CH═CH—C_(m)H_(2m)— -nVm —C_(n)H_(2n)—CH═CH—C_(m)H_(2m+1) -N- N≡C— -N —C≡N -S- S═C═N— -S —N═C═S -F- F— -F —F -CL- Cl— -CL —Cl -M- CFH₂— -M —CFH₂ -D- CF₂H— -D —CF₂H -T- CF₃— -T —CF₃ -MO- CFH₂O— -OM —OCFH₂ -DO- CF₂HO— -OD —OCF₂H -TO- CF₃O— -OT —OCF₃ -A- H—C≡C— -A —C≡C—H -nA- C_(n)H_(2n+1)—C≡C— -An —C≡C—C_(n)H_(2n+1) -NA- N≡C—C≡C— -AN —C≡C—C≡N On the left only in combination On the right only in combination - . . . n . . . - —C_(n)H_(2n)— - . . . n . . . —C_(n)H_(2n)— - . . . M . . . - —CFH— - . . . M . . . —CFH— - . . . D . . . - —CF₂— - . . . D . . . —CF₂— - . . . V . . . - —CH═CH— - . . . V . . . —CH═CH— - . . . Z . . . - —CO—O— - . . . Z . . . —CO—O— - . . . ZI . . . - —O—CO— - . . . ZI . . . —O—CO— - . . . K . . . - —CO— - . . . K . . . —CO— - . . . W . . . - —CF═CF— - . . . W . . . —CF═CF— in which n and m are each integers, and the three dots “. . .” are place-holders for other abbreviations from this table.

Besides the compounds of formula I, the mixtures according to the invention preferably comprise one or more compounds of the compounds mentioned below.

The following abbreviations are used:

(n, m and l are, independently of one another, each an integer, preferably 1 to 6, I possibly may also be 0 and preferably is 0 or 2)

TABLE D Exemplary, preferred compounds of formula I having a high ε_(⊥):

YG-n-F

YG-nO-F

YG-nO-OD

YG-n-OD

YG-n-T

YG-nO-T

YG-n-OT

YG-nO-OT

CK-n-F

B-n-m

B-n-Om

B-nO-Om

B-n-F

B-nO-F

B-n-T

B-nO-T

B-n-OT

B-nO-OT Exemplary, preferred dielectrically positive compounds

CP-n-F

CP-n-CL

GP-n-F

GP-n-CL

CCP-n-OT

CCG-n-OT

CCG-n-F

CCG-V-F

CCG-nV-F

CCU-n-F

CCEP-n-F

CCEU-n-F

CCEU-n-F

CDU-n-F

CPG-n-F

CPU-n-F

CPU-n-OXF

CGG-n-F

CGG-n-OD

CGU-n-F

PGU-n-F

GGP-n-F

GGP-n-CL

PGIGI-n-F

PGIGI-n-CL

CCPU-n-F

CCGU-n-F

CPGU-n-F

CPGU-n-OT

PPGU-n-F

DPGU-n-F

CCZU-n-F

PUZU-n-F

CCOC-n-m

CCQG-n-F

CCQU-n-F

PUQU-n-F

CDUQU-n-F

CPUQU-n-F

CGUQU-n-F

PGUQU-n-F

APUQU-n-F

DPUQU-n-F

DGUQU-n-F

CPU-n-F

DAUQU-n-F

CLUQU-n-F

ALUQU-n-F

DLUQU-n-F

LGPQU-n-F Exemplary, preferred dielectrically neutral compounds

CC-n-m

CC-n-Om

CC-n-V

CC-n-Vm

CC-n-mV

CC-n-mVI

CC-V-V

CC-V-mV

CC-V-Vm

CC-Vn-mV

CC-nV-mV

CC-nV-Vm

CC-n-VV

CC-n-VVm

CVC-n-V

CVC-n-Vm

CP-n-m

CP-n-Om

PP-n-m

PP-n-Om

CCP-n-m

CCP-n-Om

CCP-V-m

CCP-nV-m

CCP-Vn-m

CCP-nVm-I

CPP-n-m

CPG-n-m

CGP-n-m

PGP-n-m

PGP-n-mV

PGP-n-mVI

CCZPC-n-m

CPPC-n-m

CGPC-n-m

CPGP-n-m Exemplary, preferred dielectrically negative compounds

CY-V-n

CY-V-On

CY-nV-m

CY-nV-Om

CY-Vn-m

CY-Vn-Om

CY-nVm-I

CY-nVm-OI

PY-V-n

PY-V-On

PY-nV-m

PY-nV-Om

PY-Vn-m

PY-Vn-Om

PY-nVm-I

PY-nVm-OI

CCY-V-n

CCY-V-On

CCY-nV-m

CCY-nV-Om

CCY-Vn-m

CCY-Vn-Om

CCY-nVm-I

CCY-nVm-OI

CPY-V-n

CPY-V-On

CPY-nV-m

CPY-nV-Om

CPY-Vn-m

CPY-Vn-Om

CPY-nVm-I

CPY-nVm-OI

CY-n-m

CYn-Om

CVY-n-m

CVY-V-n

CZY-n-Om

COY-n-m

COY-n-Om

Y-n-m

Y-n-Om

Y-nO-Om

PY-n-m

PY-n-Om

CCY-n-m

CCY-n-Om

CCY-n-mOI

CCZY-n-Om

CCOY-n-m

CCOY-n-Om

CPY-n-m

CPY-n-Om

PYP-n-m

CP(F,Cl)-n-Om

CLY-n-m

CLY-n-Om

ACQU-n-F

Table E shows chiral dopants which are preferably employed in the mixtures according to the invention.

TABLE E

C 15

CB 15

CM 21

R S-811/S-811

CM 44

CM 45

CM 47

CN

R-1011/S-1011

R-2011/S-2011

R-3011/S-3011

R-4011/S-4011

R-5011/S-5011

In a preferred embodiment of the present invention, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table E.

Table F shows stabilizers which can preferably be employed in the mixtures according to the invention in addition to the compounds of formula I. The parameter n here denotes an integer in the range from 1 to 12. In particular, the phenol derivatives shown can be employed as additional stabilizers since they act as antioxidants.

TABLE F

In a preferred embodiment of the present invention, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table F, in particular one or more compounds selected from the group of the compounds of the following two formulae

EXAMPLES

The following examples explain the present invention without restricting it in any way. However, the physical properties make it clear to the person skilled in the art what properties can be achieved and in what ranges they can be modified. In particular, the combination of the various properties which can preferably be achieved is thus well defined for the person skilled in the art.

COMPOUND EXAMPLES

Exemplary compounds having a high dielectric constant perpendicular to the director (∈_(⊥)) and a high average dielectric constant (∈_(av.)) are exemplified in the following compound examples.

Compound Examples 1.1 and 1.2

Compounds of formula I-1 are e.g.

This compound (CK-3-F) has a melting point of 85° C., a Δ∈ of −8.4 and an ∈_(av.) of 13.4.

This compound (CK-5-F) has a phase sequence of K 74° C. N (63.7° C.) I, a Δ∈ of −7.8 and an ∈_(av.) of 12.2.

Compound Example 2

A compound of formula I-2 is e.g.

This compound (YG-2O-F) has a melting point of 69° C., a Δ∈ of only +1.0 and an ∈_(av.) of already 13.4.

Compound Examples 3 and 4

Compounds of formula I-3 are e.g.

This compound (B-2O-O5) has a melting point of 57° C., a Δ∈ of −13.7 and an ∈_(av.) of even 17.9.

This compound (B-4O-O5) has similar preferably properties.

Compound Example 5

A compound of formula I-4 is e.g.

This compound (B-5O-OT) has a melting point of 64° C., a Δ∈ of only −3.7 and an ∈_(av.) of even 18.6.

MIXTURE EXAMPLES

In the following are exemplary mixtures disclosed.

Example 1

The following mixture (M-1) is prepared and investigated.

Mixture 1 Composition Compound Concentration No. Abbreviation /% by weight 1 CY-3-O4 14.0 2 CK-3-F 6.0 3 CK-5-F 6.0 4 B-2O-O5 5.5 5 YG-2O-F 5.0 6 CCY-3-O1 8.0 7 CCY-3-O2 12.0 8 CCY-3-O3 12.0 9 PUQU-3-F 11.0 10 DGUQU-4-F 8.0 11 CDUQU-3-F 6.5 12 APUQU-3-F 6.0 Σ 100.0 Physical properties T(N, I) = 78.0° C. n_(e)(20° C., 589 nm) = 1.5927 Δn(20° C., 589 nm) = 0.1147 ∈_(∥)(20°, 1 kHz) = 20.5 ∈_(⊥)(20°, 1 kHz) = 14.0 Δ∈(20°, 1 kHz) = 6.5 ∈_(av.)(20°, 1 kHz) = 16.2 γ₁(20° C.) = 342 mPa · s k₁₁(20° C.) = 12.0 pN k₂₂(20° C.) = 6.5 pN k₃₃(20° C.) = 14.0 pN V₀(20° C.) = 1.42 V

This mixture, mixture M-1, has a dielectric ratio (∈_(⊥)/Δ∈) of 2.2 and is characterized by a very good transmission in an FFS display and shows a very short response time.

Example 2

The following mixture (M-2) is prepared and investigated.

Mixture 2 Composition Compound Concentration No. Abbreviation /% by weight 1 CY-3-O4 20.0 2 CK-4-F 6.0 3 CK-5-F 10.5 4 CCY-3-O1 8.0 5 CCY-3-O2 12.0 6 CCY-3-O3 10.0 7 PUQU-3-F 12.0 8 DGUQU-4-F 8.0 9 CDUQU-3-F 6.0 10 APUQU-3-F 7.5 Σ 100.0 Physical properties T(N, I) = 79.0° C. n_(e)(20° C., 589 nm) = 1.5816 Δn(20° C., 589 nm) = 0.1058 ∈_(∥)(20°, 1 kHz) = 19.6 ∈_(⊥)(20°, 1 kHz) = 12.3 Δ∈(20°, 1 kHz) = 7.2 ∈_(av.)(20°, 1 kHz) = 14.7 γ₁(20° C.) = 325 mPa · s k₁₁(20° C.) = 11.9 pN k₂₂(20° C.) = t.b.d. pN k₃₃(20° C.) = 14.9 pN V₀(20° C.) = 1.35 V Remark: t.b.d.: to be determined.

This mixture, mixture M-2, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.7 and is characterized by a good transmission in an FFS display and shows a short response time.

Example 3

The following mixture (M-3) is prepared and investigated.

Mixture 3 Composition Compound Concentration No. Abbreviation /% by weight 1 CY-3-O2 8.0 2 CY-3-O4 15.0 3 CK-3-F 6.0 4 CCY-2-1 12.5 5 CCY-3-O1 7.0 6 CCY-3-O2 12.0 7 CCY-3-O3 8.0 8 PUQU-3-F 12.0 9 DGUQU-4-F 7.0 10 CDUQU-3-F 6.0 11 APUQU-3-F 6.5 Σ 100.0 Physical properties T(N, I) = 79.0° C. n_(e)(20° C., 589 nm) = 1.5838 Δn(20° C., 589 nm) = 0.1060 ∈_(∥)(20°, 1 kHz) = 17.3 ∈_(⊥)(20°, 1 kHz) = 10.9 Δ∈(20°, 1 kHz) = 6.4 ∈_(av.)(20°, 1 kHz) = 13.0 γ₁(20° C.) = 297 mPa · s k₁₁(20° C.) = 11.9 pN k₂₂(20° C.) = t.b.d. pN k₃₃(20° C.) = 15.3 pN V₀(20° C.) = 1.43 V Remark: t.b.d.: to be determined

This mixture, mixture M-3, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.7 and is characterized by a good transmission in an FFS display and shows a short response time.

Example 4

The following mixture (M-4) is prepared and investigated.

Mixture 4 Composition Compound Concentration No. Abbreviation /% by weight 1 CY-3-O4 15.0 2 YG-2O-F 6.0 3 ACQU-3-F 12.5 4 CCQU-3-F 8.0 5 CLY-2-1 10.0 6 CCY-3-O2 10.0 7 CCOY-3-1 15.0 8 CGG-3-OD 15.0 9 DGUQU-2-F 3.0 10 DGUQU-4-F 5.5 Σ 100.0 Physical properties T(N, I) = 80.0° C. n_(e)(20° C., 589 nm) = 1.5798 Δn(20° C., 589 nm) = 0.1036 ∈_(∥)(20°, 1 kHz) = 16.1 ∈_(⊥)(20°, 1 kHz) = 9.7 Δ∈(20°, 1 kHz) = 6.5 ∈_(av.)(20°, 1 kHz) = 11.8 γ₁(20° C.) = 287 mPa · s k₁₁(20° C.) = 12.0 pN k₂₂(20° C.) = 6.6 pN k₃₃(20° C.) = 15.0 pN V₀(20° C.) = 1.44 V

This mixture, mixture M-4, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.5 and is characterized by a good transmission in an FFS display and shows a short response time.

Example 5

The following mixture (M-5) is prepared and investigated.

Mixture 5 Composition Compound Concentration No. Abbreviation /% by weight 1 CGG-3-OD 21.0 2 PUQU-2-F 4.0 3 CCZU-2-F 4.0 4 CCZU-3-F 14.0 5 APUQU-3-F 5.0 6 CC-3-V 4.0 7 YG-2O-F 5.0 8 CY-3-O4 6.0 9 CY-5-O2 10.0 10 CCY-3-O2 9.0 11 CCY-5-O2 9.0 12 CZY-3-O2 9.0 Σ 100.0 Physical properties T(N, I) = 78.0° C. n_(e)(20° C., 589 nm) = 1.5818 Δn(20° C., 589 nm) = 0.1045 ∈_(∥)(20°, 1 kHz) = 14.6 ∈_(⊥)(20°, 1 kHz) = 9.4 Δ∈(20°, 1 kHz) = 5.2 ∈_(av.)(20°, 1 kHz) = 11.2 γ₁(20° C.) = 211 mPa · s k₁₁(20° C.) = 11.0 pN k₂₂(20° C.) = 6.7 pN k₃₃(20° C.) = 14.7 pN V₀(20° C.) = 1.52 V

This mixture, mixture M-5, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.8 and is characterized by a good transmission in an FFS display and shows a short response time.

Example 6

The following mixture (M-6) is prepared and investigated.

Mixture 6 Composition Compound Concentration No. Abbreviation /% by weight 1 CC-3-V 11.0 2 YG-2O-F 6.0 3 CY-3-O4 18.0 4 ACQU-3-F 6.5 5 CCP-3-OT 5.5 6 CCP-3-1 5.0 7 CCY-3-O2 10.0 8 CCY-5-O2 10.0 9 CGG-3-OD 15.0 10 APUQU-3-F 2.0 11 DGUQU-2-F 3.0 12 DGUQU-4-F 8.0 Σ 100.0 Physical properties T(N, I) = 79.5° C. n_(e)(20° C., 589 nm) = 1.5782 Δn(20° C., 589 nm) = 0.1016 ∈_(∥)(20°, 1 kHz) = 14.5 ∈_(⊥)(20°, 1 kHz) = 8.3 Δ∈(20°, 1 kHz) = 6.2 ∈_(av.)(20°, 1 kHz) = 10.4 γ₁(20° C.) = 180 mPa · s k₁₁(20° C.) = 11.9 pN k₂₂(20° C.) = 6.0 pN k₃₃(20° C.) = 14.1 pN V₀(20° C.) = 1.46 V

This mixture, mixture M-6, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.3 and is characterized by a good transmission in an FFS display and shows a short response time.

Example 7

The following mixture (M-7) is prepared and investigated.

Mixture 7 Composition Compound Concentration No. Abbreviation /% by weight 1 CC-3-V 17.0 2 YG-2O-F 6.0 3 CY-3-O4 18.0 4 CCP-3-OT 8.0 5 CCP-3-1 2.0 6 CCY-3-O2 12.0 7 CCY-5-O2 8.0 8 CGG-3-OD 15.0 9 APUQU-3-F 3.0 10 DGUQU-2-F 3.0 11 DGUQU-4-F 8.0 Σ 100.0 Physical properties T(N, I) = 75.5° C. n_(e)(20° C., 589 nm) = 1.5766 Δn(20° C., 589 nm) = 0.0997 ∈_(∥)(20°, 1 kHz) = 13.1 ∈_(⊥)(20°, 1 kHz) = 8.0 Δ∈(20°, 1 kHz) = 5.2 ∈_(av.)(20°, 1 kHz) = 9.7 γ₁(20° C.) = 151 mPa · s k₁₁(20° C.) = 11.5 pN k₂₂(20° C.) = t.b.d. pN k₃₃(20° C.) = 13.7 pN V₀(20° C.) = 1.58 V Remark: t.b.d.: to be determined

This mixture, mixture M-7, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.5 and is characterized by a good transmission in an FFS display and shows a short response time.

Example 8

The following mixture (M-8) is prepared and investigated.

Mixture 8 Composition Compound Concentration No. Abbreviation /% by weight 1 CC-3-V 25.0 2 CY-3-O2 1.0 3 B-5O-OT 7.0 4 CCY-3-O1 11.0 5 CCY-3-O2 13.0 6 CCY-3-O3 15.0 7 PUQU-3-F 10.0 8 CCQU-3-F 10.0 9 CDUQU-3-F 8.0 Σ 100.0 Physical properties T(N, I) = 95° C. n_(e)(20° C., 589 nm) = 1.5679 Δn(20° C., 589 nm) = 0.0937 ∈_(∥)(20°, 1 kHz) = 11.2 ∈_(⊥)(20°, 1 kHz) = 7.5 Δ∈(20°, 1 kHz) = 3.6 ∈_(av.)(20°, 1 kHz) = 8.7 γ₁(20° C.) = 161 mPa · s k₁₁(20° C.) = 14.7 pN k₂₂(20° C.) = 7.4 pN k₃₃(20° C.) = 16.6 pN V₀(20° C.) = 2.11 V

This mixture, mixture M-8, has a dielectric ratio (∈_(⊥)/Δ∈) of 2.1 and is characterized by a very good transmission in an FFS display and shows a very short response time.

Example 9

The following mixture (M-9) is prepared and investigated.

Mixture 9 Composition Compound Concentration No. Abbreviation /% by weight 1 CC-3-V 13.0 2 CCP-3-1 10.0 3 CK-3-F 6.0 4 CK-4-F 5.0 5 CK-5-F 8.0 6 CCY-2-1 16.0 7 CCY-3-1 14.0 8 CGG-3-F 11.0 9 PUQU-3-F 6.0 10 CDUQU-3-F 7.0 11 APUQU-3-F 4.0 Σ 100.0 Physical properties T(N, I) = 90.5° C. n_(e)(20° C., 589 nm) = 1.5781 Δn(20° C., 589 nm) = 0.0972 ∈_(∥)(20°, 1 kHz) = 10.8 ∈_(⊥)(20°, 1 kHz) = 7.2 Δ∈(20°, 1 kHz) = 3.6 ∈_(av.)(20°, 1 kHz) = 8.4 γ₁(20° C.) = 182 mPa · s k₁₁(20° C.) = 14.1 pN k₂₂(20° C.) = t.b.d. pN k₃₃(20° C.) = 17.0 pN V₀(20° C.) = 2.08 V Remark: t.b.d.: to be determined.

This mixture, mixture M-9, has a dielectric ratio (∈_(⊥)/Δ∈) of 2.0 and is characterized by a good transmission in an FFS display and shows a very short response time.

Example 10

The following mixture (M-10) is prepared and investigated.

Mixture 10 Composition Compound Concentration No. Abbreviation /% by weight 1 Y-3-O1 6.0 2 B-2O-O5 6.0 3 CC-3-V 10.5 4 YG-2O-F 6.0 5 CCP-3-OT 6.5 6 CCP-V-1 17.0 7 CCP-V2-1 7.0 8 CGP-3-2 5.0 9 CGG-3-F 15.0 10 CCY-3-O2 10.0 11 APUQU-3-F 3.0 12 DGUQU-4-F 8.0 Σ 100.0 Physical properties T(N, I) = 79° C. n_(e)(20° C., 589 nm) = 1.6005 Δn(20° C., 589 nm) = 0.1103 ∈_(∥)(20°, 1 kHz) = 11.7 ∈_(⊥)(20°, 1 kHz) = 7.0 Δ∈(20°, 1 kHz) = 4.7 ∈_(av.)(20°, 1 kHz) = 8.6 γ₁(20° C.) = 117 mPa · s k₁₁(20° C.) = 11.3 pN k₂₂(20° C.) = 6.5 pN k₃₃(20° C.) = 14.4 pN V₀(20° C.) = 1.61 V

This mixture, mixture M-10, has a dielectric ratio (∈_(⊥)/Δ∈) of 1.5 and is characterized by a good transmission in an FFS display and shows a short response time.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments and examples are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

The entire disclosures of all applications, patents and publications, cited herein and of corresponding EP Application No. 15001057.7, filed Apr. 13, 2015, and EP Application No. 15001531.1, filed May 21, 2015, are incorporated by reference herein. 

1. A liquid-crystalline medium having a nematic phase and a dielectric anisotropy (Δ∈) of 0.5 or more, said medium having a dielectric constant perpendicular to the director (∈_(⊥)) in the range of 2 or more to 8 or less and at the same time a ratio of the dielectric constant perpendicular to the director (∈_(⊥)) to the dielectric anisotropy (Δ∈), i.e. (∈_(⊥)/Δ∈) of 1.0 or more or a dielectric constant perpendicular to the director (∈_(⊥)) of 8 or more and a dielectric anisotropy (Δ∈) of 26 or less.
 2. The medium according to claim 1, wherein said medium has a dielectric constant perpendicular to the director (∈_(⊥)) in the range of 2 or more to less 8 or less and at the same time a ratio of the dielectric constant perpendicular to the director (∈_(⊥)) to the dielectric anisotropy (Δ∈), i.e. (∈_(⊥)/Δ∈) of 1.0 or more.
 3. The medium according to claim 1, wherein said medium has a dielectric constant perpendicular to the director (∈_(⊥)) of 8 or more and a dielectric anisotropy (Δ∈) of 26 or less.
 4. The liquid-crystalline medium according to claim 3, wherein said medium has a ratio of the dielectric constant perpendicular to the director (∈_(⊥)) to the dielectric anisotropy (Δ∈), i.e. (∈_(⊥)/Δ∈) of 1.0 or more.
 5. The liquid-crystalline medium according to claim 1, wherein said medium has a dielectric constant perpendicular to the director (∈_(⊥)) of 20 or less.
 6. The liquid-crystalline medium according to claim 5, wherein said medium comprises one or more compounds having a high dielectric constant perpendicular to the director (∈_(⊥)) and a high average dielectric constant (∈_(av.)).
 7. The medium according to claim 1, wherein said medium comprises one or more compounds having a high dielectric constant perpendicular to the director (∈_(⊥)) and a high average dielectric constant (∈_(av.)), which are compounds of formula I,

in which

denotes

denotes

n denotes 0 or 1, R¹¹ and R¹² independently of each other denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, each having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, and R¹¹ alternatively denotes R¹ and R¹² alternatively denotes X¹, R¹ denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms, and X¹ denotes F, Cl, fluorinated alkyl, fluorinated alkenyl, fluorinated alkoxy or fluorinated alkenyloxy, the latter four groups having 1 to 4 C atoms.
 8. The medium according to claim 7, wherein the total concentration of the compounds of formula I in the medium as a whole is 1% or more to 60% or less.
 9. The medium according to claim 1, wherein said medium further comprises one or more chiral compounds.
 10. An electro-optical display or electro-optical component comprising a liquid-crystalline medium according to claim
 1. 11. The display according to claim 10, wherein said display is based on the IPS- or FFS mode.
 12. The display according to claim 10, wherein said display contains an active-matrix addressing device.
 13. A method of generating an electro-optical effect comprising applying voltage to a display according to claim
 10. 14. The display according to claim 10, wherein said display is a mobile display.
 15. A process for the preparation of a liquid-crystalline medium according to claim 1, comprising mixing one or more compounds of formula I with one or more additional mesogenic compounds. 